1. Field of the Invention
This invention relates to the automatic focusing operation of a camera, and more particularly to a photographing lens focusing device.
2. Description of the Prior Art
If, in a macro-photographing operation using an automatic focusing camera, it is intended to focus the photographing lens on the object at the closest focusing distance merely displacing the photographing lens in the direction of the optical axis, then it is necessary that, after the photographing lens has been displaced to focus on an object at an ordinary photographing distance, the photographing lens is further displaced to focus on the object at the closest focusing distance. That is, the amount of displacement of the photographing lens is large. Accordingly, the displacement detecting member, the displacement limiting member and the drive mechanism are necessarily intricate in construction. Furthermore, as it takes a relatively long time to displace the photographing lens, the time interval which lapses from the time instant that the shutter is released until the shutter is actually opened is also relatively long, which makes it rather difficult to perform the photographing operation.
Futhermore, a method of moving a close-up lens in front of the photographing lens with an automatic focusing function auxiliary used may be employed. However, in this case, the construction of the camera necessarily becomes intricate. Therefore, employment of the method is not practical.
On the other hand, there has been a demand for realization of the technique that, where it is required to take a picture of an object at a distance shorter than the close-up photographing distance limit, e.g. 0.8 m, in the range of ordinary photographing distances, the photographing lens can be focused on the object without using high photographing technique, i.e., by changing the close-up photographing distance limit directly (skipping over the intermediate distance) to a closest focusing distance of 0.4 m for instance at the sacrifice of continuity.